1. Field of the Invention
The invention relates to a thermoplastic clamping ring having an U-shaped cross-section, designed for the clamping of covers on barrels, with a clamping lever, pivoted on one end of the thermoplastic clamping ring, and with a clamping link, which is held pivotably on the other end of the thermoplastic clamping ring and is also held pivotably in flanges of the clamping lever.
2. Description of the Prior Art
A thermoplastic clamping ring of this type is known from the DE-OS No. 25 24 631 (German Offenlegungsschrift No. 25 24 631). Such a thermoplastic clamping ring is placed on the mating flanges of the barrel body and the cover and is tensioned in the circumferential direction, and thereby draws fast the barrel cover on the barrel body in that these flanges are tensioned within the profile of the clamping ring and are drawn against each other. In order to avoid a weakening of the clamping effect, high stiffness is necessary not only in the circumferential direction, but the profile of the thermoplastic clamping ring must possess a high permanent stiffness, in order to avoid an expanding of the profile of the thermoplastic clamping ring so that the flanges of the barrel body and of the cover are kept firmly upon each other.
The FR-OS No. 2 261 197 (Gallay S.A., French Pat. No. 2261197) describes a clamping ring consisting of sheet metal, the profile of which is strengthened by beads. However, such beads are not suitable for a thermoplastic clamping ring.
Such a thermoplastic clamping ring has a smaller stiffness than a clamping ring consisting of steel. Nevertheless, a thermoplastic clamping ring is required if for reasons of corrosion or for reasons of the purefood law simple steel rings or galvanized or tempered steel rings cannot be used. In order to reach the same stiffness as a steel clamping ring, a thermoplastic clamping ring needs, at least, the four-fold wall thickness, as is evident from calculations. That leads to an extremely high material consumption and a correspondingly high price of the thermoplastic clamping ring. The connection, free from play, and, nevertheless, stable connection of the pivoting parts with the thermoplastic ring is difficult.